Recently, in-house or other types of wireless LANs have been spreading along with the improvement of wireless LAN technologies. Although not requiring troublesome line connections which are needed for a wired LAN, a wireless LAN requires various types of settings for wireless connection. Especially, settings on security, which are absolutely indispensable for the wireless LAN, are specialized and complicated and therefore difficult for general users not familiar with the technology. For example, IEEE Standard 802.11i defines a connection procedure including two elements of authentication and key generation, and has a precondition that a client and an authentication server or an access point (AP) have common information for authentication beforehand. In order to more widely spread in-house wireless LANs, simplification of the setting procedure is one of the unavoidable issues.
Methods conventionally proposed in order to solve this problem will be now described.
A first method is for performing mutual authentication between an AP and a client using wireless communication (see patent document 1). According to the first method, buttons which are installed on both sides are pushed simultaneously to lower the wireless output power on both sides. Thus, the devices are put into a special setting mode and settings are performed automatically. The first method controls the wireless output power to generate a certain type of secret communication between an AP and a client so as to perform mutual authentication and settings.
A second method is for performing mutual authentication between a master and a slave using wireless communication (see FIG. 35 and patent document 2). According to the second method, a master and a slave share a common key beforehand. For starting authentication, an authentication request is transmitted from the slave to the master. The master transmits a challenge instruction to the slave. The slave transmits an authentication request including a challenge encrypted by a common key to the master. The master decrypts the encrypted challenge by its own common key. When the decrypted challenge matches the challenge already transmitted to the slave, the master returns a response indicating that the authentication is verified or not verified to the slave in accordance with an instruction from the user.
A third method is for performing mutual authentication between a master and a slave using wireless communication (see FIG. 36 and patent document 3). The third method is performed as follows. A master and a slave each receive pushing of a registration button. The slave transmits a registration application including its own public key and inherent information to the master. The master transmits a registration confirmation including the inherent information of the slave, which is encrypted by the public key of the slave, to the slave. Then, the master transmits an authentication notification including a common key of the master, which is encrypted by the public key of the slave, to the slave. The slave transmits an authentication receipt including an authentication response, which is encrypted by a common key of the master, to the master.
A fourth method is for performing mutual authentication between two communication devices each including display means using wireless communication (see FIG. 37 and patent document 4). The fourth method is performed as follows. A communication device A transmits a key transmission message including its own public key to a communication device B. The public key is converted into another value by each of the communication device A and the communication device B, and is output using visual means or audial means of each of the communication devices. The user checks whether or not the values of the public key converted and output match each other and determines whether or not to verify the authentication. When the authentication is verified, the communication device B transmits new key generation information encrypted by the public key of the communication device A to the communication device A. Then, the communication device A and the communication device B generate a common encryption key for communication based on the new key generation information.
Patent document 1: Japanese Laid-Open Patent Publication No. 2004-215232
Patent document 2: Japanese Patent No. 3585422
Patent document 3: Japanese Patent No. 3628250
Patent document 4: Japanese Patent No. 3552648